The present invention relates to mattress foundations, and particularly to box spring mattress foundations. Mattress foundations are commonly used in combination with mattresses to complement a mattress' resiliency and/or raise a mattress to a comfortable height from a floor. The support characteristics of mattress foundations are an important factor in the performance and marketability of such foundations.
Rigid mattress foundations, while providing a comfortable sleeping position when combined with a proper mattress, have significant drawbacks. One such example is the rigid mattress foundation disclosed in U.S. Pat. No. 4,535,494 of Diamonstein. To some consumers, the simple lack of resilient support means implies uncomfortable sleep characteristics. This belief may stem from a consumer's perception while sitting on the edge of a mattress/rigid foundation combination, wherein the concentrated body load and lack of foundation deflection may overload the mattress resilient support. Such overloading of the mattress results in an undesirable "bottoming out" effect, whereby the cushioning capacity of the mattress is diminished.
Conventional box springs represent an improvement over rigid mattress foundations. One such box spring uses an array of springs, disposed between a rigid wood lower frame structure and a wire grid upper frame structure, to provide resilient support which complements the deflection of a mattress. While the propensity to overload a mattress is hereby diminished, this box spring design also has drawbacks. For instance, the presence of a great number of metal springs results in a box spring which is relatively heavy and expensive to manufacture. Also, the array of metal springs may be undesirably noisy when weight is shifted on the overlying mattress. In addition, the upper wire grid can be bent if any spring is overly stressed, producing a sagging upper frame structure or uneven support surface to support the mattress.
The prior art has attempted to solve these weight, expense, and comfort problems, but never with completely satisfactory results. For example, U.S. Pat. No. 4,100,631 of Slone attempts to defeat the weight and expense problems by using rigid upper and lower mattress foundation frames of wood, separated by resilient springs. While the Slone box spring does require fewer springs than a comparable conventional box spring, it is subject to inadequate performance under some conditions. Even though the rigid upper frame serves to distribute a centrally-located load well, such as that occurring when a user reclines, the Slone box spring does not react as well to a peripherally-located load. Under a peripheral loading, such as that occurring when a user sits on the edge of the box spring, the Slone upper rigid frame may be unable to adequately distribute a heavy load, thereby overtaxing the springs supporting that portion of the periphery where the load is applied.
While the prior art also attempts to defeat the expense and weight problems through means of resilient foam blocks in place of the springs, this method too has drawbacks. For instance, U.S. Pat. No. 4,191,991 of Morgan places foam blocks around the periphery of a mattress foundation. While these resilient foam supports greatly reduce box spring weight, the gaps between the foam blocks will create weak, unsupported "dead" spots along the periphery of the foundation. Moreover, foam supports characteristically do not exhibit a suitably long service life in most instances. Specifically, the foam supports may tend to lose some resilience and become permanently compressed after a period of use. Such functional degradation is undesirable in a mattress foundation. Similarly, the Slone patent suggests the use of foam rubber as a resilient support for a mattress foundation.
Yet another disadvantage of prior mattress foundations arises from the usual construction at the periphery of the box spring. As explained above, foundations utilizing springs to support the periphery may appear too springy or soft when a user sits thereupon. Furthermore, conventional box springs typically place only a thin cloth apron around the vertical peripheral surfaces of the foundation, resulting in the sagging and loose wrinkling of the apron when the periphery of the mattress foundation is depressed. Moreover, the thin fabric apron on conventional box springs gives users the impression that the interior of the foundation is hollow and nonsubstantial. This impression undermines the perceived quality of a mattress foundation.
Other mattress foundations are disclosed in U.S. Pat. No. 4,662,015 to Galumbeck and U.S. Pat. No. 2,992,443 to Winikoff.
In light of these disadvantages in the prior art, one objective of the present invention is to provide a long-lasting mattress foundation having relatively few springs, a relatively low weight, and a reduced manufacturing cost.
Another object of this invention is to provide a mattress foundation which better distributes loads across the width and length of the foundation, and provides a firmer suspension at the periphery of the foundation.
Yet another object of this invention is to provide a mattress foundation with a smooth, continuous, substantial vertical surface around the skirt of the foundation which will resist sagging and loose wrinkling when the foundation is loaded at the periphery.
Still another object of this invention is to provide a mattress foundation which affords quiet resilient support for an overlying mattress and its occupants.
An additional object of this invention is to provide finer manufacturing control over the suspension characteristics of a mattress foundation than is possible with conventional box springs.
Other objects will be apparent from the detailed description of the present invention.